/* -*- mode: c++; indent-tabs-mode: nil -*- */
/*
  ReferenceHolder.h

  Smart pointer like class that dereferences
  obtained pointer to a QoreReferenceCounter in its destructor.

  Qore Programming Language

  Copyright (C) 2006 - 2015 Qore Technologies

  Permission is hereby granted, free of charge, to any person obtaining a
  copy of this software and associated documentation files (the "Software"),
  to deal in the Software without restriction, including without limitation
  the rights to use, copy, modify, merge, publish, distribute, sublicense,
  and/or sell copies of the Software, and to permit persons to whom the
  Software is furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  DEALINGS IN THE SOFTWARE.

  Note that the Qore library is released under a choice of three open-source
  licenses: MIT (as above), LGPL 2+, or GPL 2+; see README-LICENSE for more
  information.
*/

#ifndef QORE_REFERENCE_HOLDER_H_
#define QORE_REFERENCE_HOLDER_H_

#include <stdlib.h>

//! a templated class to manage a reference count of an object that can throw a Qore-language exception when dereferenced
/** the destructor will call deref(ExceptionSink *)
    @code
    ReferenceHolder<QoreQFont> holder(self->getReferencedPrivateData(CID_QFONT, xsink), xsink);
    // the call to deref(ExceptionSink *) is automatic when the object goes out of scope
    if (*xsink)
       return 0;
    return holder->styleHint();
    @endcode
*/
template<typename T = class AbstractQoreNode>
class ReferenceHolder {
private:
   DLLLOCAL ReferenceHolder(const ReferenceHolder&); // not implemented
   DLLLOCAL ReferenceHolder& operator=(const ReferenceHolder&); // not implemented
   DLLLOCAL void* operator new(size_t); // not implemented, make sure it is not new'ed
      
   T* p;
   ExceptionSink* xsink;

public:
   //! creates an empty ReferenceHolder
   DLLLOCAL ReferenceHolder(ExceptionSink* xsink_) : p(0), xsink(xsink_) {}

   //! populates with object with data and the ExceptionSink pointer
   DLLLOCAL ReferenceHolder(T* p_, ExceptionSink* xsink_) : p(p_), xsink(xsink_) {}

   //! calls deref(ExceptionSink *) on the pointer being managed if not 0
   DLLLOCAL ~ReferenceHolder() { if (p) p->deref(xsink);}

   //! returns the pointer being managed
   DLLLOCAL T* operator->() { return p; }

   //! returns the pointer being managed
   DLLLOCAL T* operator*() { return p; }

   //! assigns a new pointer to the holder, dereferences the current pointer if any
   DLLLOCAL void operator=(T *nv) {
      if (p)
         p->deref(xsink);
      p = nv;
   }

   //! releases the pointer to the caller
   DLLLOCAL T* release() {
      T *rv = p;
      p = 0;
      return rv;
   }

   //! returns true if a non-0 pointer is being managed
   DLLLOCAL operator bool() const { return p != 0; }
      
   //! returns a pointer to the pointer being managed
   DLLLOCAL T** getPtrPtr() { return &p; }

   //! returns a reference to the ptr being managed
   DLLLOCAL T*& getRef() { return p; }
};

//! manages a reference count of a pointer to a class that takes a simple "deref()" call with no arguments
/**

   @code
   SimpleRefHolder<QoreStringNode> str(new QoreStringNode(QCS_UTF8));
   // QoreString::concatUnicode() can raise a Qore-language exception if the code is invalid
   str->concatUnicode(code, xsink);
   return *xsink ? str.release() : 0;
   @endcode
*/
template<typename T>
class SimpleRefHolder {
private:
   DLLLOCAL SimpleRefHolder(const SimpleRefHolder&); // not implemented
   DLLLOCAL SimpleRefHolder& operator=(const SimpleRefHolder&); // not implemented
   DLLLOCAL void* operator new(size_t); // not implemented, make sure it is not new'ed
      
   T* p;

public:
   DLLLOCAL SimpleRefHolder() : p(0) {}
   DLLLOCAL SimpleRefHolder(T* p_) : p(p_) {}
   DLLLOCAL ~SimpleRefHolder() { if (p) p->deref(); }
      
   DLLLOCAL T* operator->() { return p; }
   DLLLOCAL T* operator*() { return p; }
   DLLLOCAL void operator=(T *nv) {
      if (p)
         p->deref();
      p = nv;
   }
   DLLLOCAL T *release() {
      T *rv = p;
      p = 0;
      return rv;
   }
   DLLLOCAL operator bool() const { return p != 0; }
};

#endif
// EOF
